Rolling mill and process for rolling tubes



July 21, 1931. J. ROEDER ET AL 1,815,367

ROLLING MILL AND PROCESS FOR ROLLING TUBES I Filed June 1, 192a 2 Sheets-Sheet 1 INVENTORS JULIUS ROEDER WILHELM WELLMANN 5; 27262 '7' a 2Zaf 2yS Jdly 21, 1931. J. ROEDER ET AL 1,815,867

ROLLING MILL ANP PROCESS FOR ROLLING TUBES Filed June 1, 1928 2 Sheets-Sheet 2 INVENTORS JULIUS ROEDER I I TE WILHELM WELLMANN M by iizez'r aiiorrzqys development of the method described in Pat Patented July 2 1, 1931 UNITED STATES PATENT oFFicE;

JULIUS ROEDER AND WILHELI WEILMANN, 0F WITTEN,- GERMANY ROLLING MILL AND PROCESS FOR ROLLING TUBES Application filed June 1, 1928, Serial No. 282,201, and in Germany August 20, 1927.

Our invention relates to rolling mills and methods used in rolling tubes, especially tubes of the smaller diameters; Morespe cifically, this invention relates to a further ent N 0. 1,626,481, granted to us April 26th, 1927.

Among the objects of the invention may be mentioned reducing to a minimum the number of passes required at the finishing rolls- Where tubes of small diameter and small wall thickness are rolled, increasing the production of finished tubes, and making possible the economical production of tubes of the smaller sizes.

With a view to accomplishing these objects,

we have combined certain well-known types and wall thickness of the finished tube.

of mills, examples of such combinatlons being illustrated in the accompanying drawings, wherein j Figure 1 is a diagrammatic layout of a mill constructed in accordance with the mvention, and

Fig. 2 is a diagrammatic layout of another form of mill which is also constructed in accordance with the invention.

Methods heretofore in use for producing small tubes, from about 2 external diameter to the smaller sizes, have consisted in first producing by means of a sc-called Swedish rolling mill, or the like, a tube whose wall thickness does not exceed a predetermined dimension depending upon the desired i ilzle e preliminary tube thus produced is then reheated, and is brought to the desired finished dimensions by means of a succession of reducing mills. It has not been possible for the rolling mills heretofore employed to roll down the wall thickness of the pierced round sufiiciently to make the smallest sizes of tubes: that is to say, finished tubes such as gas pipe with a wall thickness of approximately Furthermore, in the tube mills heretofore employed, the individual mills are'not joined directly to the installations producing the pierced round, because the temperature of the pierced round after its formation is not suificient under present practice to permit a further reduction of size without reheating. It has, therefore, been customaryto use the very expenslve c'old drawing process for reducing the wall thickness. After cold drawing it has also been customary to reheat the tube and then'to reduce it to the desired finished dimensions. The cold drawing and reheating processes increase the production costs of small diameter pipes (gas pipes for example) and the process cannot result in a low-price commercial commodity.

A further disadvantage, which has seriously limited production, has been the necessity for resetting the rolls employed in existing continuous rolling mills where many successive stand of rolls are employed. Such rearrangement, andthe accurate determination of the roll setting, requires considerable time and causes lengthy breaks in operation. It is, therefore, exceedingly expensive.

Previous arrangements have not permitted the production of two or more sizes of tubes on a single sequence of reducing trains at the same time, or with a single roll set ting. On the contrary it is new necessary to roll the different tube sizes in separate operations: that is to say, having reduced a certain quantity of one tube size, it is then necessary to reset the rolls before another size can be rolled. Thus if it is desired to reduce severallsizes of tubes, without changing the roll setting, it is necessary, according to present practice, to have several reducing trains each with its separate reheat furnace. Thus each reduction is preceded by'a reheat operation, or, in the case of the smaller diameters of tubes, by a cold drawing operation and also by a reheating. This requires very extensive and expensive plants, and results in high operating costs and makes the cost of producing the tubes very high. This is precisely What the product here considered cannot hear. I

Patent No. 1,626,481, describes a method by which thin walled tubes may be rolled in 9 a few passes without-a considerable cooling of the tube, simply by reason ofthe rapid operation of the few passes required. We have discovered that the heat remaining in the tube after rolling as described in the aforei 65 that the tube may be removed after it has said patent is quite sufficient for the tube to undergo an extensive further reduction.

According to the present invention the limitations' inherent in present practice are overcome by arranging several reducing trains at intervals in line behind the finishing mill employed according to the aforewithout resetting the rolls or inserting'dif ferent sizes of rolls. The wall thickness is, of course, controlled by the finishing mill, which is here illustrated asa Swedish rolling mill. The arrangement of mills is such that after'passing through anyone of the reducing. mills thetube can be removed at that point. It is, therefore, possible to secure different degrees of reduction of the pierced round according as the-same is allowed to traverse one, a selected number, or all of themills- The number of'possible reductions in any mill train will, therefore, correspond with the number of reducing mills in the train.

In Figure 1 there are illustrated finishing mills a a and conveyor 0 upon which the heated tubes may be placed after leaving the finishing mill and when ready for the reducmg operation. A series of reducing tralns b, b b b, b, b, are shown spaced at intervals, Conveyors a, 0 0 c c, 0 and 0, are disposed between the mills a a. and the respectlve reducmg'trains and serve to con- Vey the tubes from the finishing mills a a to the first reducingtrain band from one reducing train to the next. (2, d d d, d and 03 are placed adjacent to the conveyers c c c 0, c and 0", respectively.

The smallest size of pipe which can be economically rolled over a mandrelis about 2 to 2%" in diameter. The present arrangement will therefore be applicable only for the smaller tube sizes.

and may be considered. In this case the roll trains are so related that the tube is first rolled to a diameter of 2 and is then placed upon the conveyor 0. In passing through the train I) it is reduced to 1%," external diameter; without appreciable increase in' the wall thickness given it by the finishing rolls. If a smaller diameter is desued, the tube coming from the reducing train b is allowed to runthrough the reducmg tram b and is there reduced to 1 ex- .ternal diameter. By passing the tube coming from the reducing train 12 through the reducing trainb a 1" tube is obtained. The

reducing train 6 will. produce a ,4,, tube,

. the train. I) a tube and the train. 6 a 7 tube. The arrangement is such, however,

Cooling benches For example tubes. such as gas p1pes of diameters between 1 been reduced to any of these diameters which is desired and before entering the next roll train. To accomplish this the tube is merely removed 'sidewise from the conveyor over which it is traveling (as 0 to the adjacent cooling bench (as (1*) It is clear from the example, which has just been given, that the present arrangement makes it possibleto roll several sizes of pipe (in this case six different external diameters) Without making any special adjustment of the reducing'rolls, or specially reset- 4 ting any of the reducing trains. It will also be obvious that this arrangement may be set for larger dimensions as for instance 3", 2%", 2 2 2 and 1%". It is also evident that tubes for other purposes than for use as gas pipes may be rolled according to this method. Finally it will be seen that a larger or smaller number of reducing trains than that given in the example maybe emthe installation of a suflicient number of roll trains to operate as above described in producing a sufiicient variety of tube diameters.

Figure 2 illustrates an cxampleof such a combination.- Four reducing trains 6, b b and 6 are shown aligned behind-each other. The operation of the first three trains maybe exactly like that described in the above discussion of Figure 1. That is to say, a'first reduction to 1 diameter, a second reduction to 1 4" diameter and a third reduction to 1" diameter. In the present case the reducing trains b, b, and bare not altered. However, the reducing train 6 may be so constructed that it may be set for rollin a tube or if desired a'f-t" or a tu e instead. f e It willbe clear from the foregoing description of the form illustrated inFig. 2 that such an arrangement will permit the rolling to four tube sizes at any time without makinig1 changes in the roll set up. To produce a fthor a sixth size it is only necessary to reset the rolls of one roll train.

We claim:

1. A tube rolling mill for, roducing small diameter tubes from tubes o predeterminedwall thickness coming hot from a Swedish rolling mill, comprising a plurality of reducing trains arranged in series one behind rolls in said final train to provide a pass of adjustable sizes.

2. A process for producing small diameter tubes comprising rolling a tube to a predetermined diameter and wall thickness on a Swedish rolling mill over a mandrel, taking the hot tube from the Swedish rolling mill, and rolling it through a plurality of reducing mill trains arranged in series.

ranged in series to eflI'ect the desired degree of reduction.

4. A process for producing small diameter tubes comprising rolling a tube to a predetermined diameter and wall thickness, on a Swedish rolling mill over a mandrel, taking the hot tube from the Swedish rolling mill, rolling it, without reheating, through a lurality of reducingmill trains arrange in series, and varying the setting of the last train in the series to eflect the desired degree of reduction.

In testimony whereof we have signed our names to this specification. JULIUS ROEDER.

WILHELM WELLMANN. 

